The subnanosecond motions of tryptophyl residues in peptides and proteins will be measured using time dependent fluorescence depolarization techniques based on a synchronously pumped dye laser system. The results will be related to protein structure and function, to recent crystallographic studies of thermal motion in proteins, and to theoretical models. The photophysics and photochemistry of tryptophan both in solution and in simple peptides will be studied by picosecond absorption and emission spectroscopy. Changes in the excited state properties will be measured as a function of tryptophan environment and the results applied to the use of tryptophan as an intrinsic probe for protein conformation and structure.